1. Field of the Invention
The present invention relates to an optical cross-connect apparatus for switching paths of light signals, and in particular, to an optical cross-connect apparatus for supervising quality and management information of light signals of which paths are switched and its signal supervising method.
2. Description of the Prior Art
An optical cross-connect system for switching paths of light signals transmitted into a system is equipped with an optical cross-connect apparatus (hereafter, abbreviated as OXC) having a light switch (Switch: hereafter, abbreviated as SW). It is possible to switch paths of large-capacity light signals by applying to this cross-connect system the wavelength division multiplex (hereafter, abbreviated as WDM) technology for multiplexing a plurality of signals of mutually different wavelength components. Various research and development on OXC equipped with optical SW are underway focusing attention on easiness of setting up a signal path, efficiency of protection and so on toward the information and communication age of increasingly larger-capacity (Chungpen Fan, xe2x80x9cExamining an integrated solution to optical transport networking.xe2x80x9d, Wavelength Division Multiplexing: (The first ever European meeting place for WDM Systems, Network, Marketing and Engineering Professionals), November 1997, London pp. 18-23).
FIG. 32 represents, as a concept, configuration of an optical cross-connect system to which such OXC is applied. An optical cross-connect system is equipped with a plurality of OXC, and is connected by an optical fiber transmission path on which light signals are mutually transmitted. Here, it has OXC 101 to 106, and for instance, OXC 101 is connected with OXC 102 via optical fiber transmission path 111, with OXC 105 via optical fiber transmission path 115, and with OXC 106 via optical fiber transmission path 116 respectively. Also, OXC 104 for instance is connected with OXC 103 via optical fiber transmission path 113 with OXC 105 via optical fiber transmission path 114, with OXC 106 via optical fiber transmission path 118, and OXC 106 is connected with OXC 103 via optical fiber transmission path 107 respectively.
On operating an optical cross-connect system, in order to maintain the system reliability, it is necessary to supervise light signals that are switchable to various paths and manage transmission signals inside the system by each OXC as shown in FIG. 32. For instance, there are many transmission paths for light signals transmitted from point A to point B. Therefore, each OXC supervises paths, quality states and so on of light signals, sets paths of light signals and avoids failure occurrence points. To be more specific, in OXC 101, 106, 103 and 104, a service signal transmitted from point A to point B on path 12 indicated by dashed lines in FIG. 32 supervises transmitted light signals as to their respective quality and management information 131, 132, 133 and 134 if included in them.
FIG. 33 represents an overview of conventional OXC for supervising quality and management information of such light signals. This OXC has light signal input terminals 201 to 20n (n is a natural number of 2 or more) to which light signals are inputted, nxc3x97n light SW21 for having light signals inputted from n pieces of input port corresponding to each of these light signal input terminals 201 to 20n outputted from any one of n pieces of output port and switching their paths, light signal detecting section (hereafter, abbreviated as DET) for detecting quality of light signals outputted from n pieces of output port of nxc3x97n light SW21 and management information included therein, light signal output terminals 231 to 23n to which light signals outputted from each of n pieces of output port of nxc3x97n light SW21 are outputted, light signal supervising section (hereafter, abbreviated as SV) 24 for supervising quality and management information of light signals from the output ports detected by DET 221 to 22n and control section (hereafter, abbreviated as CNT) 25 for controlling path switching of nxc3x97n light SW21 from supervising results of SV24.
nxc3x97n light SW21 arbitrarily connects n pieces of input port with n pieces of output port according to a control signal from CNT25. DET221 to 22n output light signals outputted from each output port of nxc3x97n light SW21 as-is and detect various signal states by branching a part of them. Such detecting functions of DET are a light signal level detecting function, a signal-to-noise (hereafter, abbreviated as SN) ratio detecting function, a light reproduction and overhead (hereafter, abbreviated as OH) detecting function, and alight reproduction and OH terminating function. As prescribed by the Synchronous Digital Hierarchy (hereafter, abbreviated as SDH) and the Synchronous Optical Network (hereafter, abbreviated as SONET) for instance, this OH has information on frame synchronization, error supervising, maintenance, operation and so on inserted in a predetermined position of light signals composed in a frame of a predetermined format.
In conventional OXC of such configuration, light signals inputted from light signal input terminals 201 to 20n are inputted in n pieces of input port of nxc3x97n light SW21 respectively, and as a result of path switching performed according to a control signal from CNT25, they are outputted from any one of n pieces of output port of nxc3x97n light SW21. And the light signals outputted from n pieces of output port of nxc3x97n light SW21 have their quality and management information included in them detected at DET221 to 22n respectively, and are also outputted from light signal output terminals 231 to 23n. Such detected information is supervised at SV24, and SV24 instructs CNT25 to change path setting for instance from the results of supervising. CNT25 outputs a control signal responding to this instruction from SV24 to nxc3x97n light SW21, and switches the path of light signals inputted from the input ports.
As a technology on OXC for supervising such light signals, in addition to this, the Japanese Patent Laid-Open No. 5-183509 xe2x80x9cLight Switch and Optical Channelxe2x80x9d for instance discloses a technology to perform path cutting or path setting for a light SW that supervises light signals branched on the one hand by a branching device provided per signal line and switches paths of light signals branched on the other hand by the branching device.
Object of the Invention
However, the conventionally proposed OXC required DET for detecting information to be supervised from light signals for each one of n pieces of output port of a light SW, leading to larger size of OXC. Furthermore, as optical communication will increasingly spread and light signals will be of larger capacity, the number of ports of a light SW is destined to increase, and thus it becomes necessary to install additional DET to meet the increase, further leading to larger size and higher cost of OXC.
Thus, an object of the present invention is to provide OXC that is, even in the case where a light SW becomes large-seized, capable of supervising quality and management information of light signals passing through inside the apparatus with low-cost configuration.
In the present invention, an optical cross-connect apparatus includes: light switch means having n (n is a natural number of 2 or more) pieces of first port and at least (n+1) pieces of second port, which switches paths of light signals inputted from each of said first ports and has them outputted from any one of said second ports; light path control means for branching a path of said light switch means so as to have light signals inputted from any one of said first ports outputted from any two of said second ports; and light signal supervising means for supervising quality of light signals outputted from either of said two ports.
To be more specific, it includes light switch means having n pieces of first port and at least (n+1) pieces of second port, and by light path control means, it branches a path so as to have light signals inputted from any one of said first ports outputted from any two of said second ports. And by light signal supervising means, it supervises quality of light signals outputted from either of said two ports.
In the present invention, an optical cross-connect apparatus includes light switch means having n (n is a natural number of 2 or more) pieces of first port and at least (n+1) pieces of second port, which switches paths of light signals inputted from each of said first ports and has them outputted from any one of said second ports, light path control means for branching a path of said light switch means so as to have light signals inputted from any one of said first ports outputted from any two of said second ports, light amplifying means for amplifying light signals outputted from either of said two ports, and light signal supervising means for supervising quality of light signals amplified by this light amplifying means.
To be more specific, the optical cross-connect apparatus includes light amplifying means for amplifying light signals outputted from the light switch means at a previous stage to the light signal supervising means. This can change a branching ratio between light signals to be supervised inputted in the light signal supervising means and signals outputted from the other second ports so that even if the levels of signals to be supervised become lower, the levels of light signals to be originally transmitted become correspondingly higher, and thus it allows an optical cross-connect apparatus of high reliability with a supervising function to be provided.
In the present invention, an optical cross-connect apparatus includes light switch means having a plurality of first and second ports, which switches paths of light signals inputted from each of said first ports and has them outputted from any one of said second ports, light path control means for branching a path of said light switch so as to have light signals inputted from any one of said first ports outputted from any two of said second ports when supervising said light signals and have light signals inputted from each of said first ports outputted from predetermined one of said second ports when not supervising said light signal, and light signal supervising means for supervising quality of light signals outputted from either of said two ports only when performing said supervising.
To be more specific, the present invention provides light switch means having a plurality of first and second ports, and by light path control means, it has light signals inputted from any one of the first ports outputted from any two of the second ports when supervising light signal, and on the other hand, it has light signals inputted from each of the first ports outputted from predetermined one of the second ports when not supervising said light signal. And it supervises, by light signal supervising means, quality of light signals outputted from either of said two ports only when performing supervising.
In the present invention, an optical cross-connect apparatus includes a wavelength separating means for separating, per wavelength component, wavelength multiple light wherein light signals of a plurality of mutually different wavelength components are multiplexed, light switch means having n (n is a natural number of 2 or more) pieces of first port and at least (n+1) pieces of second port, which switches light signals of the respective wavelength components separated by said wavelength separating means inputted from each of said first ports and has them outputted from any one of said second ports, light path control means for branching a path of said light switch means so as to have light signals inputted from one of said first ports outputted from any two of said second ports, light signal supervising means for supervising quality of light signals outputted from a predetermined third port of said two ports, wavelength component converting means for converting each individual light signal outputted from said second ports excluding said third port into a light signal of predetermined wavelength components, and wavelength multiplexing means for multiplexing per predetermined number these light signals converted by the wavelength component converting means.
To be more specific, the present invention provides an input stage of light switch means for an optical cross-connect apparatus with wavelength separating means for separating, per wavelength component, wavelength multiple light wherein light signals of a plurality of mutually different wavelength components are multiplexed, and supervises light signals by having a path of the light switch means branched by light path control means, and on the other hand, it provides an output stage of the light switch means with wavelength component converting means for converting each individual light signal outputted from any port other than a supervising port into a light signal of predetermined wavelength components, and it multiplexes a light signal of each of wavelength components per predetermined unit by wavelength multiplexing means to output them.
Moreover, in the present invention, an optical cross-connect apparatus is characterized by said light signal supervising means that detects and supervises management information placed in an overhead section of a predetermined frame format.
Moreover, in the present invention, the above optical cross-connect apparatus is characterized by said light path control means that sets a path for having light signals to be supervised inputted from each port outputted from said two ports per port in order.
Furthermore, in the present invention, an optical cross-connect apparatus includes light switch means having a plurality of first and second ports, which switches paths of light signals inputted from each of said first ports and has them outputted from any one of said second ports and also switches paths of light signals inputted from each of said second ports and has them outputted from any one of said first ports, n pieces of upward light signal input and output terminals, n pieces of downward light signal input and output terminals, a first light circulator provided corresponding to each of said first ports for outputting upward light signals inputted from each of the upward light signal input terminals to each corresponding port of said first ports and also outputting downward light signals inputted from each of said ports to said downward light signal output terminal, a second light circulator provided corresponding to each of said second ports for outputting downward light signals inputted from each of the downward light signal input terminals to each corresponding port of said second ports and also outputting upward light signals inputted from each of said ports to said upward light signal output terminal, light path control means for branching a path of said light switch means so as to have light signals inputted from any one of said first ports outputted from any two of said second ports and also have light signals inputted from any one of said second ports outputted from any two of said first ports, a first light signal supervising means for supervising quality of light signals outputted from a predetermined third port of any two of said first ports, and a second light signal supervising means for supervising quality of light signals outputted from a predetermined fourth port of any two of said second ports.
To be more specific, the present invention provides each port of light switch means having a plurality of first and second ports with first and second light circulators, each of which performs two-way path switching of upward and downward light signals. And it has a path of light switch means branched by the light path control means to have upward and downward light signals supervised by direction respectively by the light signal supervising means.
Moreover, in the present invention, an optical cross-connect apparatus is characterized by said first and second light signal supervising means that detect and supervise management information placed in an overhead section of a predetermined frame format.
To be more specific, the present invention detects and supervises management information placed in an overhead section of a predetermined frame format, such as those prescribed by SDH and SONET.
Moreover, in the present invention, the optical cross-connect apparatus is characterized by said light path control means that sets a path for having light signals to be supervised inputted from any first or second port outputted from any two of said second or first ports per port in order.
To be more specific, as the paths of the light switch means are branched per port in order, the optical cross-connect apparatus can supervise light signals inputted from any port with one detecting means and one supervising means for supervising light signals even in the case where the apparatus becomes large-sized with additional ports.